Fluid control valve

Abstract

A linear solenoid-type flow control valve with a valve element position feedback loop. An input consisting of an analog command signal is supplied in the form of a serial digital signal from a modulating transmitter through an optical fiber transmission line. An actuator operating driving circuit, a receiving demodulator for reconverting the light signal from the transmission line to the serial digital signal and further to the analog command signal and supplying it to the driving circuit, a differential transformer for detecting an operated position of a control valve element and a feedback circuit from the differential transformer are integrally mounted on the coupling component of the control valve element and its actuator and in this way the component parts at the receiving side are arranged as close as possible with respect to one another.

We claim: 
     
       1. In a fluid control valve including a driving circuit for generating a drive signal corresponding to an analog command signal indicative of a flow rate or fluid pressure, an actuator adapted to be operated by said drive signal, a control valve element operable in response to the operation of said actuator, a position sensor for detecting an output position of said actuator, and a feedback circuit responsive to said actuator output position detected by said position sensor to control said drive signal so as to attain said flow rate or fluid pressure indicated by said command signal, the improvement comprising: a modulating transmitter for converting said analog command signal to a serial digital signal and converting said serial digital signal to a light signal;   a transmission line including an optical fiber cable for transmitting said light signal; and   a receiving demodulator for reconverting said light signal to said serial digital signal, reconverting said serial digital signal to said analog comand signal and supplying said analog command signal to said driving circuit;   whereby said receiving demodulator, said driving circuit, said actuator, said control valve element, said position sensor and said feedback circuit are mounted integrally thereby arranging close to each other said driving circuit and said actuator, said position sensor and said feedback circuit and said feedback circuit and said driving circuit, respectively, wherein said modulating transmitter includes an analog-digital converter for converting said analog command signal to said serial digital signal, a modulator for pulse-duration modulating or pulse-frequency modulating said serial digital signal, and an electro-light convertor for converitng the output signal of said modulator to said light signal, wherein said modulator includes a pulse oscillator for generating clock pulses having a predetermined frequency, a counter for repeating counting of said clock pulses with the same number of positions as a serial digital signal to be transmitted, and a digital comparator for applying to said electro-light convertor a data indicative of a comparison between a serial digital data and a count of said counter, and wherein said receiving demodulator includes a light-electro convertor for converting said light signal from said transmission line to said serial digital signal, and a low-pass filter for demodulating said analog command signal from said serial digital signal generated from said light-electro convertor.   
     
     
       2. A fluid control valve according to claim 1, further comprising a thermo-sensor for detecting a temperature of said control valve element or a working oil thereof, and wherein said driving circuit includes another feedback circuit for controlling said drive signal in accordance with said detected temperature.